My current '01 Sub has the Delco electromagnetic fluid stuff that works extremely well, but not looking forward to their eventual replacement (AFAIK no other alternatives yet).
But a really good board for Chevy truck stuff is:
http://www.oursuv.com/boards/GMSUV0407/index.html
A couple of people on that board like the IAS stuff. Post the question there and you'll get lots of responses.
Also, one of the Board's members has a Topics website for Chevy Suburbans that's very comprehensive:
http://aplsweb.com/Topics/Topics.htm